The Joker's Revenge — Carolyn Keene

NANCY AND HER PALS GO UNDERCOVER IN CHICAGO'S MOST EXCLUSIVE DEPARTMENT STORE

Mischief is in fashion at the Danner & Bishop department store, and the owner suspects foul play. The only clue is a playing card--a joker--left behind at the scene of every "accident." It's up to Nancy to catch the crooked card player before the game gets out of hand.

Surrounded by the world's most expensive jewelry and furs, Nancy discovers that the sabotage is an inside job. She's playing a dangerous game in which the stakes are high and the joker is wild--a game in which the winner takes all!